A classic sign of a sticky or stuck caliper is that one of the two pads is much more worn than the other. Likewise if as you say the pair of pads is much more worn than the other side of the car, it's probably stuck.

Otherwise, if you see any brake fluid on/around the caliper, it's most likely shot. Replacing a caliper is not too hard, but it can be a PITA to get the old flex lines off without munging them up, and likewise, when you are trying to get the thread started on the flex line into the new caliper by rotating the caliper, it can also be a PITA - those calipers get heavy with one hand holding the caliper and the other the brake line while you are trying to get the thread started. But overall not too difficult of a job.

Rebuilding a caliper is somewhat of an academic exercise IMHO, as today you can get "loaded" rebuilt calipers from most parts houses for reasonable money. It can be a pain to pop the piston(s) put in new seals, and hope the bores are in good shape to continue with, not to mention cleaning all the accumulated gook.

I won't lecture on the fact that you should probably change the pair of calipers rather than just one, but it'll work with just one new one.

And changing fluid every other year is very good practice. Get a Motive Power pressure bleeder, it makes the job very easy, far easier than the ol' Mitey Vac.

Rgds,
Chris W.